This invention relates to irrigation sprinklers, and more particularly to a new and improved vandal resistant and self-aligning locking device for releasably coupling the nozzle housing of a part-circle pop-up sprinkler to the rotary pop-up stem.
In U.S. Pat. No. 4,681,259 issued to Troup et al. Jul. 21, 1987, entitled ROTARY DRIVE SPRINKLER, there is disclosed a pop-up part-circle sprinkler comprising a sprinkler housing within which a rotary drive mechanism is disposed, and including a reversing mechanism including a fixed trip dog and an adjustable trip dog. The rotary drive mechanism operates to rotate a nozzle assembly including a nozzle housing threadably coupled to the upper end of a rotary pop-up stem. Mounted within the nozzle housing is a dual bore nozzle from which water streams are ejected through an aperture in the side wall of the nozzle housing, the water being supplied to the nozzle through the tubular stem from a suitable water supply source coupled to the sprinkler housing.
During assembly of the nozzle housing to the pop-up stem of the sprinkler disclosed in the aforementioned patent, it is important that the nozzle housing be properly aligned relative to the stem to ensure that the discharge outlet from the nozzle is in a predetermined rotational position relative to the fixed trip dog of the reversing mechanism forming part of the sprinkler drive mechanism so that when assembled, the rotary position of the nozzle at one extreme of its rotary motion limits can be fixed and accurately determined from the nozzle housing. Toward this end, as disclosed in the aforementioned patent, timed threads are employed for the connection between the nozzle housing and the upper end of the tubular stem. While the use of timed threads has proved generally satisfactory, it has been found that in some instances, during assembly of the nozzle housing onto the tubular stem, over tightening of the nozzle housing may occur, thereby resulting in the nozzle rotary position being off-set relative to the desired fixed position with respect to the fixed trip dog.
Another problem which has arisen is that the use of a simple threaded connection between the nozzle housing and tubular stem does not prevent vandals from unthreading the nozzle from the stem. Sprinklers of the type disclosed in the aforementioned patent are frequently used in areas subject to vandalism such as public parks, playing fields, and the like, and it is desirable to construct such sprinklers in a manner to deter vandalism.
As will become more apparent hereinafter, the present invention provides a vandal resistant locking device for releasably coupling the nozzle housing to the tubular riser of a rotary pop-up sprinkler such as disclosed in the aforementioned patent, and which eliminates the necessity for timed threads while ensuring that the nozzle housing will always be assembled on the stem with the nozzle outlet in the desired fixed rotary position with respect to the fixed internal trip dog.